Gametogenesis, Fertilization and Parthenogenesis 



189 



Carbohydrate was later found in purified fer- 

 tilizin (Tyler, '42) and in electrophoretically 

 homogeneous gelatinous coat (Runnstrom 

 et al., '42) of sea urchins. From this and 

 later work (Tyler, '48a,b, '49; Krauss, '49; 

 Vasseur, '48a,b, '49) it has become clear that 

 fertilizin is a complex of amino acids and 

 sugars that may be termed a glycoprotein. 



A procedure for the preparation of elec- 

 trophoretically homogeneous sea urchin fer- 

 tilizin is outlined in Table 11. Some of the 

 analytical data obtained (Tyler, '48a,b, '49) 

 on such preparations of fertilizin of the sea 



Upon electrophoresis the fertilizins of E. 

 cordatum (Runnstrom et al., '42) and of 

 5. purpuratus (Tyler, '48a, '49) migrate 

 towards the anode at pH values as low as 

 pH 2. This highly acidic character is prob- 

 ably correlated with the high content (ca. 

 25 per cent) of sulfate found by Vasseur 

 ('47) in E. esculentus and confirmed by Ty- 

 ler ('48b) in S. purpuratus. Upon ultracen- 

 trifugation of a jelly coat solution of 

 Psammechinus, Runnstrom et al. ('42) found 

 a main component with a sedimentation 

 constant of 2.9 X lO"!^ varying with con- 



T< 



Fig. 59. Eggs of the sea urchin Strongylocentrotus purpuratus, photographed in Syracuse dishes, X Via- a. Un- 

 treated egg-suspension. b,\S minutes after addition of a solution of antifertilizin. (From Tyler, '40b.) 



urchin Strongylocentrotus purpuratus are 

 given in Table 12. The values given there 

 for amino acids and reducing sugars are 

 probably low, since some of these very likely 

 contribute to the humin residue that forms 

 upon acid hydrolysis. By means of paper 

 chromatography Vasseur and Immers ('49) 

 find differences in the sugar components of 

 the hydrolyzed jelly coat of different species 

 of sea urchins; namely galactose in Echinus 

 esculentus, fucose in Echinocardium corda- 

 tum, fucose and galactose in Strongylocen- 

 trotus droebachiensis, fucose and glucose in 

 Paracentrotus lividus. The amino acids have 

 also been investigated by microbiological 

 methods, but there is as yet insufficient evi- 

 dence to indicate whether or not different 

 species differ in this respect too. It is prema- 

 ture to conclude that specificity of the fer- 

 tilizins is dependent upon differences in par- 

 ticular sugar or amino acid constituents. 

 Even when the constituents are the same, 

 differences in configuration of the molecule 

 may determine specificity of action, as ap- 

 pears to be the situation with immune anti- 

 bodies. 



centration in the manner indicative of non- 

 spherical molecules. With active fertilizin of 

 5. purpuratus a sedimentation constant of 

 6.3 X 10-13 has been obtained (Tyler, '49). 

 The molecular weight is evidently, then, 

 greater than 82,000, which would be the 

 value for spherical shape. 



Antifertilizins from Sperm. The substance 

 on the surface of the sperm with which 

 fertilizin reacts has been termed antifer- 

 tilizin. Frank ('39) and Tyler ('39a) were 

 able to extract such a substance from the 

 sperm of sea urchins and the keyhole limpet, 

 by means of brief heating or freezing and 

 thawing. It is also extractable (Tyler and 

 O'Melveny, '41) by slight acidification of 

 the suspension. It can be assayed by its 

 ability to neutralize the agglutinating ac- 

 tion of fertilizin on sperm. Another manifes- 

 tation of its activity is its ability to 

 agglutinate a suspension of eggs (Fig. 59). 

 In so doing it causes a precipitation mem- 

 brane to form on the surface of the gelati- 

 nous coat of the egg (Fig. 60). With strong 

 solutions this membrane thickens and con- 

 tracts within a short time to the surface 



